It is common for luminaires (i.e., lighting devices) to be connected to a dimming switch or control that allows a user to lower the light level of the luminaire. Typical incandescent light sources provide light by heating a metal filament. When an incandescent light source is dimmed, whether by lowering the source voltage or by altering the phase or duty cycle of the power signal, not only does the brightness of the light decrease, but the light changes to a warmer (redder) color as the temperature of the filament decreases. The correlation between change in color and temperature is typically approximated within a chromaticity space by a black body curve (i.e., Planckian locus).
Solid state luminaires, such as LED lights, do not produce light by heating a filament. When the power source of an LED light is diminished, the brightness of the LED decreases but the color of the LED does not appreciably change.